Prolonged dry weather conditions bring the potential for potassium deficiency, especially in soybeans that require a lot of potassium, and remove up to 1.4 lb. per bushel.
Potassium is vital to plant health as it regulates the opening and closing of pores (leaf stomata) on the plant’s surfaces that allow gases and water vapor to pass through. Without enough potassium, these pores are slower to respond to environmental conditions and may take longer to close meaning poorer regulation of water potential and greater susceptibility to drought.
Potassium depends on adequate soil water to move from high concentration on soil surfaces to areas of low concentration near plant roots. When the soil is dry, the diffusion rate of potassium decreases to a point that deficiency symptoms may appear. Dry conditions also limit root growth so there is less capacity for the plant to take up potassium.
Recognizing the symptoms
One of the key nutrients for plant health, potassium moves very easily throughout the plant and signs of deficiency show up first on lower leaves, and progress towards the top of the plant as deficiency increases. Deficiency can be seen from the V3 stage up to the more advanced vegetative stages in older leaves. The most common sign of potassium deficiency in soybeans appears as yellowing along the leaf margin. In more severe cases, deficiency symptoms can progress to the upper leaves of the plant, where leaves become scorched and die back, and ultimately drop off the plant.
Learn more about the problems a potassium deficiency can cause at nutrien-ekonomics.com.